1. Field of the Invention
This invention relates to a video recording device, a video reproducing device and a video recording/reproducing device and; more particularly, is suitably applicable to a digital video tape recorder (VTR) which is developed mainly for home use other than for use in broadcasting stations.
2. Description of the Related Art
A digital video tape recorder (VTR) is proposed for home use rather than for broadcasting station use. This type of digital video tape recorder has been required to increase the recording efficiency of image signals in order to miniaturize the size, thereby digital image signals are compressively coded to record and reproduce. An orthogonal transformation coding method such as Discrete Cosine Transform (DCT) has been used as the compression algorithm.
In the orthogonal transformation coding method such as DCT, it is required that inputted video signals are partitioned into blocks of, for example 8.times.8 pixels for the sake of compression processing. Therefore, it is proposed that the recording region of the video signals is defined as the region which is composed of an integral multiple of a block of 8 pixels.times.8 lines. For instance, on the number of scanning lines, with regard to the 525-line formation video signals, 480 lines are defined as the recording region, on the other hand, 576 lines in the 625-line formation video signals are defined as the recording region. Thus, the tape-format of a digital VTR for the purpose of home use is satisfied by merely recording the region displayed on a TV screen, so that all of the scanning lines required by the broadcasting standards will not be recorded.
This type of the digital VTR for the purpose of home use has much less deterioration of picture quality compared with an analog VTR, since the video signals are digitally recorded. Accordingly, if such digital VTR becomes applicable for broadcasting station use, a VTR for broadcasting station use can be obtained at extremely lower cost and with simple construction compared with conventional digital VTR for broadcasting station use.
However, the video signals which are required to be recorded by the broadcasting standards, e.g., 485 scanning lines of the video signals in the case of the 525-line formation or 576 and a half lines in the case of the 625-line formation, are not recorded in the digital VTR for the purpose of home use, so that it cannot be applied to broadcasting station use under the present conditions.
To solve this problem, it is considered that the number of the scanning lines be increased by an integral multiple of 8 lines, e.g., 488 scanning lines of the video signals in the case of the 525-line formation or 584 lines in the case of the 625-line formation, to satisfy the requirement of the broadcasting standards. However, as a recording method of digital VTR for the purpose of home use, there is a problem that it will take longer for compressive-coding processing and simultaneously recording efficiency will decrease, so that this is not an adequate solution.